The present invention relates to methods of continuously converting metallurgical melts, such as copper and nickel mattes, ferronickel, etc.
Known in the art is a method of continuously converting metallurgical melts by blowing them through with a gaseous oxidant in the bath of a converter furnace. The starting melt and the flux are delivered into the bath, and in successively formed zones of oxidative blasting, slag formation, and slag separation a process is realized resulting in the formation of a concentrated product and slag, which are separately tapped through holes available in the bath. Also known is a converter furnace for realizing such method, in whose roof tuyeres are mounted to feed the gaseous oxidizer, which are located at an angle of 60-80.degree. to the horizontal (USSR Inventors Certificate No. 120,646).
In this conventional converter furnace the bath has a constant depth, and the oxidizer is fed thereinto at a pressure of 4-6 atm through the tuyeres, whose nozzles are spaced 350-400 mm from the melt level in the bath, thus providing for the penetration of the oxidizer to a depth sufficient to mix the melt in the oxidative blasting zone, but not resulting in movement of the mass of the melt.
In accordance with the foregoing method of converting, the oxidizer, the flux, and the melt are fed into the front part of the furnace, the slag and the concentrate being tapped from the slag separation zone in the rear part of the furnace.
The heat transfer to the slag separation zone is effected mainly due to movement of the concentrated mass from the blasting zone, so that thermal stabilization in the zone of slag separation is only possible with the described way of discharging the concentrate and feeding the starting melt.
The starting melt must be delivered to the front part of the furnace to prevent the concentrated product from being diluted with the starting melt.
In the previous method the melt circulation is most intense in the front part of the furnace, and it is in this part that the melt is being actively treated by the oxidizer and the flux. However, due to the constant depth of the bath, and supply of the gaseous oxidizer in the direction of the slag separation zone, there occurs attenuation of the melt circulation, with movement of the melt in the end of this zone taking place only on account of drainage of the process products. As a result, the transfer of heat released in the oxidative blasting zone to the zone of slag separation is not secured to a sufficient extent, so that the temperature in the slag separation zone is lowered, which impedes separation of the slag and its drainage, and causes incrustations.
The low mobility of the melt in the slag separation zone does not promote isolation of its mechanical inclusions from the slag, and lowers the efficiency of the converter slag depletion.
The need to charge the flux directly into the oxidative blasting zone, resulting from poor assimilation of flux beyond this zone because of insufficient melt circulation, involves operational inconveniences including clogging of the flux spouts by the melt splashes, and the requirement to use flux of a definite grain-size composition so as to prevent it from being carried away by the exhaust gases.
In producing a conditioned product, its discharge in the end of the furnace, combined with the indispensable period of metal concentrations in the converting mass across the furnace length, which is due to the slag interaction with the concentrate, result in the need to reblow the melt in the oxidative blasting zone. Reblowing the melt increases metal losses in the slag.
In addition, due to the concentrate being discharged in the end of the furnace, the exchange reactions between the slag and the mass of the melt within the slag separation zone conform to the equilibrium composition of a rich mass, which makes effective depletion of the impossible slag.
All the cited disadvantages deteriorate the characteristics of the converting process.
Employment of the previous method is limited to its preferable use for obtaining an intermediate concentrate requiring further treatment.